The 28-year-old has been working hard to get back into shape to play Scarlett Widow in the superhero flick "Avengers Assemble", and so, she is resorting to martial arts.

"Scarlett really got into martial arts. She has also logged a lot of time toning her muscles in the gym. She likes to mix up her workouts with circuits and resistance training," contactmusic.com quoted a source as saying.

Johansson has also changed her diet.

"She's a grazer. She will have between six and eight small meals a day," the source added.